1. Field of the Invention
This invention relates to a process for obtaining soybean protein flakes and/or granules of agreable taste suitable for the direct human consumption, easily digestible and almost devoided of the flatulence.
2. Description of the Prior Art
As known, the necessary components of a complete nurishement are the proteins, the lipids and the glucydes.
As to the proteinic influence of a nurishment, the soybean seeds, especially if defatted, allow several advantages.
Consequently, soybean is adopted as a feeding source high in vegetable proteins. However, it is unpleasant to the human palate, so that it cannot because as it is without further handling with other substances and their consequent cooking (in order to get wurstels, hamburgers, biscuits, bread and so on).
This occurs also by using defatted and re-treated soybean meat obtained, through an extrusion process in granular form, which has been always suggested to be used in mixture with other foods which, afterwards are required to be cooked.
Many processes have been suggested for obtaining soybean protein suitable for the direct human consumption without further handlings, either in granular or flour form, or in paste form mixed with oils or fats.
In the process disclosed in the Italian patent application No. 21753A/80 the extruded granules of soybean proteins are subjected to a drying operation (dry cooking) at a temperature or between 60.degree. C. and 120.degree. C. for a period between 14 and 3 hours.
In U.S. Pat. No. 3 865 956 the defatted soybean seeds, with a moisture content lower than 17%, are heated at 150.degree.-35.degree. C. for 2-60 seconds under a pressure of 3-30/kg.cm.sup.2 and then rapidly expanded by lowering the pressure. Finally the product obtained is powdered to a particle size of about 200 microns and mixed with oils for obtaining a soybean paste. The process disclosed in the above U.S. patent is a typical extrusion process wherein the product is subjected to a very quick cooking and lightening due to the expansion.
Both these known processes lead to soybean proteins in granular or paste form when mixed with oils, ready to the direct human consumption. In fact, such processes modify the soybean proteins converting them into a product more agreable to the palate which can be eaten without further handling. However, the soybean proteins obtained by these known processes are still hard to digest if not sufficiently cooked. In fact, in both the above known processes the cooking time is not enough to get protein granules which were sufficiently cooked to be easily digestible by feeble or suffering stomachs, especially if directly eaten as such for curative purposes, for relatively long periods of time and not in small dosages.
Also a further prolongued drying, as described in the Patent application No. 21753A/80, does not improve the digestibility, but only improve the taste.
Moreover in the extruded soybean proteins, before and after the drying process, the stachiose and raffinose sugars are still present in high percentage (12 to 14%); these sugars, in fact, are not hydrolized by the two above mentioned heat-processes.
When, on the contrary, such granular soybean proteins are used as such and eaten alone in not small dosages for curative purposes (from 20 to 60 gr. daily) and for periods of a few weeks, the presence of the above sugars lead to flatulence, namely the rising of intestinal gas which is upleasantly ejected, producing considerable troubles to people eating the proteins granules as such. Therefore, the removal of the flatulence is important for a nurishment based on soy proteins to be eaten as such.
Clinical tests have pointed out that flatulence is so notable and so demoralizing, even eating in small quantities soybean proteins, that patients are induced to refuse such nurishment even after few weeks.